The present invention relates to an arrangement for driving out volatile impurities from ground water by air or another gas.
Arrangements of the above mentioned general type are known in the art. One such arrangement is disclosed for example in the German document DE-OS 3,625,488. The arrangement disclosed in this document has the advantage that, with low energy consumption due to negative pressure build up above the ground water level in a shaft, air or other gas can be aspirated than in an air receiving chamber located underneath the ground water level in the shaft, and from there can discharge through a sieve wall into the liquid and pass through the liquid in form of bubbles and thereby the volatile impurities can be removed from the ground water. It has been also proposed to form the sieve wall and nozzle plate which extends through a greater part of the shaft cross-section and carries a float. Thereby it remains always in the same and adjustable distance from the ground water level in the shaft.
It has been shown that in narrow shaft boreholes or well shafts, the arrangement of the nozzle plate extending transverse to the longitudinal axis of the shaft poses some difficulties and prevent ground water circulation produced by the throughgoing air or another gas and identified as "air lift effect".